1. Field of the Invention
The present invention relates to an airtight apparatus that comprises a package, a lid having an optical window, and an electronic device, the package and the lid bonded together, sealing the device in airtight fashion.
2. Description of the Related Art
In recent years, new apparatuses have been developed, each having a chip or substrate which is designed for use in optical communication apparatuses and optical apparatuses, such as microscopes, and which has additional components, such as lenses and mirrors, so that the apparatuses may have less components, be smaller and perform more functions. Of these apparatuses, many should be airtight-sealed and filled with inert gas or should be vacuum-sealed so that they may operate reliably or their functions may be fully performed. To achieve the airtight sealing, brazing material, particularly solder, i.e., a soft brazing material, is used in some cases. Instead of solder, flux may be used. But it is not desirable to use flux, because it may generate out gases. If solder is used, however, it may not well wet the members that are to be sealed together. That is, in this case, desirable alloy layers can hardly be formed, rendering it difficult to accomplish satisfactory airtight sealing. Therefore, there is a demand for a solder-sealing technique that can increase the wetting of solder, thereby to accomplish sufficient airtight sealing.
Airtight-sealing techniques designed to increase the wetting of solder is disclosed in, for example, Japanese Patent No. 3391123. The technique disclosed in Japanese Patent No. 3391123 will be briefly described, with reference to FIG. 7.
As FIG. 7 shows, a substrate 101 and a cap 103 define a space, in which a G sensor 105 mounted on the substrate 101 can be contained. The cap 103 is coated with solder 104, and a wire 102 is provided on the substrate 101. A heater tool 106 applies heat and pressure to the cap 103, melting solder 104 between the substrate 101 and the cap 103. The solder 104 therefore bonds the substrate 101 and cap 103 together in airtight fashion. In the technique described in the specification of Japanese Patent No. 3391123, the load exerted from the heater tool 106 to the cap 103 is of such a value that breaks the oxide films formed on the wire 102 and the solder 104, respectively. Thus, the load breaks the oxide films and achieves solder bonding, without degrading the wetting of the solder, which would occur if the oxide films would remain. As a result, the air-tightness of the sealing can be enhanced.